Photographic paper containing yellow fog-preventing agents



United States Patent 3,362,826 PHOTOGRAPHIC PAPER CGNTAINING YELLOW FOG-PREVENTING AGENTS Edith Weyde and Anita von Kt'inig, Leverkusen, and Artur Allendiirfer, Porz, near Cologne, Germany, assignors to Agfa Aktiengesellschaft, Leverkusen, Germany, a corporation of Germany No Drawing. Filed Apr. 3, 1964, Ser. No. 357,314 Claims priority, application Germany, Apr. 27, 1963, A 42,979 4 Claims. (Cl. 96-85) ABSTRACT OF THE DISCLOSURE Formation of yellow fog in barytes layer carrying lightsensitive silver halide emulsion is reduced by incorporating in barytes layer certain mercapto thiodiazoles or mercapto oxdiazoles.

Upon processing of photographic paper, especially by mechanical processes, thiosulphate frequently is carried from the fixing bath into the developing bath. In other cases, such as rapid-, stabilisingor fixing developing baths, a silver halide solvent, e.g., thiosulphate is added to the developing bath. When such thiosulphate-containing developing compositions are used in the development of photographic paper, a more or less pronounced yellow to brown fog is produced, depending on the type and age of the photographic paper. In the presence of some stabilizers, e.g., l-phenyl-S-mercapto-tetrazole, this fog may also be colored blue to blue violet. This fog consists of finely divided silver deposited in the baryteslayer.

In barytes coated photographic papers, this yellow fog is due to silver salts which migrate during casting from the emulsion into the barytes layer where they are retained by adsorption. On storage of these finished papers, these silver salts are reduced to silver, a process which takes place particularly in the first months of storage. If silver halide solvents such as thiosulphates are added to the developer during the processing of the papers, the dissolved silver salts are reduced on the silver nuclei of the barytes-coating, and yellow fog and patches are produced.

After storage, the yellow fog is particularly pronounced on areas of the paper previously exposed to atmospheric moisture, e.g., at the edges of the paper and on the top sheet of a package.

The yellow fog occurs particularly when unrinsed emulsions of silver chloride or of silver chlorobromide are used because the chlorides present in excess can form soluble silver complex salts.

The yellow fog also occurs if types of gelatine containing compounds that dissolve silver halide are used in the production of the emulsion or of the baryta layer and if in addition there are present degradation products of gelatine which forms nuclei. These types of gelatine also produce a yellow fog in photographic films.

In addition, emulsions that have not been fully ripened and which have a steep gradation also tend to produce a yellow fogging, especially if high-contrast-developers with a high content of potassium bromide are used for developing the latent silver image.

We have now found that the yellow fog can be avoided if compounds of the formula are added to the barytes layer, where W represents group ings of the formula YR in these formulae:

X is divalent suphur or oxygen Z is 1) an alkylene radical with preferably 4-8 carbon atoms;

(2) an -SAS- bridge, where A is an alkylene radical with 4-1() carbon atoms, xylylene which may be substituted by lower alkyl groups, an ether'group of the structure -CH CH (O-CH CH n being 1 to 5, or

(3) a NHBNH bridge, where B is an alkylene radical with preferably 4-10 carbon atoms, a cycloalkylene radical or an arylene radical, preferably a phenylene Y is divalent sulphur or an NH-grouping and R is an alkyl group with 6-18 carbon atoms, aralkyl such as a benzyl or a phenylathyl, cycloalkyl such as a cyclohexyl, cycloalkylaryl, or aryl preferably a phenyl. The following compounds, for example, may be used:

W: i t

Z-C C-SH Decomposition 134 Decomposition The preparation of compounds Nos. 1-2 and Nos. 6-

'18 is given in Belgian Patent No. 595,431. Compounds Nos. 3-5 can be prepared by the following method for 70 Compound No. 4: 20.2 g. (0.1 mol) suberic acid dihyprecipitated by stirring into ice cooled hydrochloric acid and filtered by suction. 15 g. of the impure crude product are purified by repeated solution in dilute sodium hydroxide and precipitation with dilute hydrochloric acid.

The preparation of Compounds Nos. 19-36 is given in Belgian Patent No. 606,550.

By adding the compounds according to the invention to the barytes layer, the production of yellow fog is prevented or its intensity reduced without alteration of the photographic properties of the photographic paper such as its sensitivity, 'y-value and image tone. The products used according to the invention are fast to diffusion and do not migrate into the silver halide gelatine layer. Thus no deleterious effect on the resulting image is observed.

The efiectiveness of the compounds according to the invention as additives to the barytes-coating was particularly surprising in view of the fact that the compounds have no or only a very slight effect in preventing yellow fog when added to other layers, e.g., the light-sensitive emulsion layer.

As binding agents for the barytes-coating can be used animal glues preferably gelatine which may be partially replaced by film-forming hydrophilic products such as polyvinyl alcohol, polyvinylpyrrolidone, alginic acid or derivatives thereof such as alkali metal salts, esters in particular with lower aliphatic glycols, or amides, and in addition carboxyethylcellulose, starch or the like.

As barytes pigment can be used mineral products such as processed heavy spar or artificial products such as permanent white or blanc fixe.

The paper treated with barytes can be coated with any silver halide emulsion. Suitable are silver chloride, bromide or mixtures thereof which may contain up to 10% of silver iodide.

The compounds according to the invention are added in the form of solutions or dispersions, e.g., in water, lower aliphatic alcohol or dirnethylformamide, to the barytes dispersions in quantities of 0.01 to 1 g. per liter, preferably 0.05 to 0.15 g. per liter.

Based on the amount of barytes the mercapto thiodiazol compounds have to be added in an amount of 0.022 g. preferably 0.1-0.8 g. per kg. lBaSO The com pounds may be added at any stage of their production to the baryte dispersion, e.g., in the kneader or mixer or before application.

T he usual combinations of developers can be used for processing the photographic papers of the invention. The process is not dependent on certain developer substances. For example, it is possible to use developers of the hydro quinone type, pyrocotechol type, p-methylaminophenol, compounds of the 1-phenylpyraZolidone-3 series, phenylenediarnine developers and the like.

Example 1 0.1 g. per liter of compound 3 dispersed in ethyl alcohol is added to a baryte dispersion having the following composition:

15.0 kg. of an aqueous dispersion of BaSO (:12 kg. BaSO 1.5 kg. of gelatine in the form of a 5% aqueous solution 0.01 l. of a 20% aqueous solution of sodium hexarnetaphosphate 0.3 l. of chrome alum 0.2 l. of milk A barytes-coating is applied on a paper support by casting three times a thin layer of the above composition onto the support.

A layer of an unrinsed silver chloride gelatine emulsion is then applied is known manner onto this barytescoated paper and dried.

A sample of the above freshly prepared paper and the above paper stored for 2 days in a heated cupboard at 60 C. are developed for l,2,3,5 and 7 minutes at 30 C. in a p-methylaminophenol-hydroquinone developer, to which 10 g. per liter crystallized sodium thiosulphate have been added to test for yellow fog. Whereas the sample of the above paper showed no yellow fogging even after storage in the heating cupboard, a control sample which was prepared as described above with the exception that no compound of the invention was added showed a slight yellow fog and the control sample stored in the heating cupboard had a brown yellow fog after a developing time of only 2 minutes. If the emulsion layer is removed from these developed papers, it is seen that the barytes-coating of the control sample is brown and that of photographic paper of the invention is colorless.

Instead of compound 3, 0.1 g. per liter of compound 5 or 0.1 g. per liter of compound 7 or 0.1 g. per liter of compound 13 or 0.07 g. per liter of compound 16 or 0.12 g. per liter of compound 12 or 0.08 g. per liter of compound 36 may be added to the casting dispersion of barytes-coating.

Example 2 0.17 g. per liter of compound 6 dispersed in ethyl alcohol is added to a barytes-dispersion and a paper is coated twice with the dispersion in known manner. A silver chlorobromide gelatine emulsion is then applied in known manner onto this barytes coated paper and dried. The test for yellow fog is carried out as described in Example 1. Whereas a yellow fog appears on the control sample after storage in the heating cupboard, no yellow fog is seen on the treated sample.

Instead of compound 6, 0.15 g. per liter of compound 12 or 0.17 g. per liter of compound 5 or 0.12 g. per liter of compound 2 or 0.1 g. per liter of compound 22 may be added to the barytes layer.

We claim:

1. A photographic paper having a barytes coating that carries a light-sensitive silver halide emulsion containing a compound of formula:

wherein X is a divalent radical of the group consisting of sulfur and oxygen and wherein W is a group selected from those having the following formulae:

l ii zo /GSH and -YR Z standing for (1) an alkylene radical having between 4 and 8 carbon atoms,

(2) the divalent radical S-AS, wherein A is a radical of the group consisting of alkylene having between 4 and 10 carbon atoms, a xylylene group and an ether group of the formula CH CH -(OCH CH where n is an integer between 1 and 5, or

(3) the divalent radical -NHBNH wherein B is a member of the group consisting of an alkylene having between 4 and 10 carbon atoms, a cycloalkylene and a phenylene,

Y standing for a divalent radical of the group consisting of sulfur and imino and R is a member of the group consisting of alkyl hav- 15 ing between 6 and 18 carbon atoms, a phenylalkyl, a cycloalkyl and a phenyl, said compound being present in an amount that reduces the formation of yellow fog. 2. A photographic paper as defined in claim 1, in which the compound has the formula:

where m is 4-8.

3. A photographic paper as defined in claim 1, in which the compound has the formula:

4. A photographic paper as defined in claim 1, in which the compound has the formula:

References Cited UNITED STATES PATENTS 2,453,346 11/1948 Russell 9661 2,514,650 7/1950 Knott et al. 9652 2,843,491 7/1958 Allen et al 96-109 3,051,570 8/1962 Dersch et a1. 96109 3,212,892 10/1965 Konig et a1. 9661 NORMAN G. TORCHIN, Primary Examiner. J. H. RAUBITSCHEK, Assistant Examiner. 

